Blind stitch sewing machine



Jan. 23, 1940- c. w. MUELLER BLIND STITCH SEWING MACHINE Original Filed May 18, 1937 6 Sheets-Sheet 1 We; 0. W. Mueller Jan. 23, 1940. c. w. MUELLER BLIND STITCH SEWING MACHINE Original Filed May 18, 1937 6 Sheets-Sheet 2 mww maiv H Czar/es VV. Mueller Moww - Jan. 23, 1940. c. w. MUELLER 2,188,228

BLIND STITCH SEWING MACHINE Original Filed May 18, 1937 s Sheets-Sheet s grwowiw Char/es W Mueller c. w. MUELLER 2,188,228

BLIND STITCH SEWING MACHINE Original Filed May 18, 1937 Jan. 23; v-

6 Sheets-Sheet 4 I vs/v T08 Mueller Jan. 23, 1940. c. w. MUELLER BLIND STITCH SEWING MACHINE Original Filed May 18, 1937 6 Sheets-Sheet 5 Char/es 14/. Mueller 6 I rod/mm Jan. 23, 1940. c. w. MUELLER BLIND STITCH SEWING MACHINE 6 Sheets-Sheet 6 Original Filed May 18, 1937 Fig.

Char/es I44 Mueller 3% SWMZ'T' Patented Jan. 1940 UNITED STATES PATENT OFFICE BLIND STITCH SEWING MACHINE Charles W. Mueller, St.-Louis, Mo.,'assignor to Lewis Invisible Stitch Machine Company, St. Louis, Mo., a corporation of Maine Original application my 18, 1931, Serial No.

Divided and this application November 12, 1937, Serial No. 114,243

9 Claims. (01. 112-176) I taining and guiding means, and bobbin thread' clamping means.

with these and other objects in view whic will more fully appear, the nature of the invention will be more clearly understood by-following the description, the appended claims, and the several views illustrated in the accompanying drawings.

In the drawings: Figure 1 is a top plan view of a sewing machine constructed in accordance with my invention,

Figure 2 is a left hand elevation thereof, parts being broken away and in section,

Figure 3 is a right hand elevation ofthe machine, the forwardly extending arm being shown in section,

Figure 4 is a horizontal section taken through the horizontal arm and the adjacent end of the laterally extending arm, the arms being shown in separated relation.

Figure 5 is a. detail rear elevation of the forwardly extending arm,

Figure 6 is a detail vertical section taken through the oil housing,

Figures '7, 8, 9 and 10 are detail views showing the take-up lever in difierent positions,

Figure 11 is a perspective view of the feed dog,

Figure 12 is a perspective view of the front end of the feed dog without the vertically yieldable needle thread, the bobbin thread, and the feed dog when the latter is at the forward end of its stroke,

Figure 17 is a similar view but showing the feed dog at the rear end 'of its stroke,

Figure 18 is a bottom plan view of the foot,

Figure 19 is a perspective view of the cloth retainer, and

Figure 20 is a perspective view of the edge uide.

Like reference numerals designate corresponding parts throughout the several figures of the drawings. I

The sewing machine as shown in the accompanying drawings, includes a main frame A which comprises a standard 5, a horizontal arm 6 ex'tending'laterally from the upper end of the standard and terminating in a forwardly and downwardly extending upper arm I, and a base arm I which extends laterally from the lower end of the standard and terminates in a forwardly extending base arm 9. The arm I is removablyconnected at its rear end to the free end of the arm ,6 by screws ll.

A substantially horizontal presser foot B is fixed to the free end of the arm 'I.

The arm I is hollow and includes a top I l, and right and left side walls l2 and I3 respectively. Rigidly supported within the arm 1 adjacent the rear end thereof and in spaced relation-to the right hand wall l2,,is a housing C for containing a lubricant such as oil. This housing comprises a bottom ll, a top It, front and rear walls I6, I! and a right hand side wall l8, forming a resultant oil compartment, the left hand side of the housing being open for the purpose of obtaming access to the interior of the housing. This open side of the housing is, however, sealed against the egress of oil by a closure plate 19 and an intermediate gasket which are remov-. ably attached to the housing by screws 2|.

As shown in Figure 4, a main shaft 22 is journaled in the horizontal arm 8 and the left end thereofterminates in spaced relation to the free end of said arm. A main shaft extension 23 extends across the rear end of the arm I and has one end journaled in the side wall 18 of the oil housing C and its other end journaled in the right hand wall 12 of the arm; The left hand end of the-shaft extension 23 projects into the oil com- 45 24. Thus it will be seen that the arm I together 50 i with the main shaft extension 23 is removable as a unit from the free end of the arm 6.

Journaled within the arm I and extending longitudinally thereof is an oscillatory needle Fixed to the front end of the shaft is u shaft 25.

a needle arm 23 which carries a curved needle 21 which reciprocates across and above an opening 28 formed in the presser foot B. The rear end of the needle shaft is operatively connected to the main shaft extension 23 by a rock arm 23 rigidly secured to the rear'end of the needle shaft, an eccentric 30 fixed to the main shaft extension 23, and a link 3! which connects the rock arm with the eccentric; It will be noted that the eccentric 30 is located between the oil housing C and the right hand wall 12 of the arm 1, and also that the penetrating stroke of the needle is from right to left.

Cooperating with the needle 21 above the foot to form lock stitches, is a rotary hook D containing a bobbin thread E which is mounted on a shaft 32 extending transversely of the arm I and joumaled in said arm adjacent the front end thereof. The hook shaft 32 is driven from the main shaft extension 23 by a shaft 33 which is joumaled in and extends diagonally and longitudinally of the arm I, there being a gear cou-- pling 34 between the hook shaft 32 and the driving shaft 33 and a gear coupling 35 between the driving shaft 33 and the main shaft extension 23, the coupling 35 including a driving gear 36 fixed to the outer end of said shaft extension. The rear end of the driving shaft is joumaled in the upper portion of the oil housing C above the main shaft extension 23, and consequently the gear coupling 35 is located within the oil compartment of the housing.

Mounted on the base arm 9 of the frame directly below the presser foot B is a post F, and supported on this post is an oscillatory ridge forming element G for projecting a ridge of fabric upwardly through the presser foot opening 28 into needle penetrating position, the element G being oscillated from the main shaft 22 in the usual manner. Also supported by the post is a vertically yieldable work clamp H which cooperates with the under face of the presser foot to clamp the fabric against the thrust of the needle.

An intermittent or 4-motion upper feed dog I is located directly in rear of the needle path and cooperates with the work clamp through the opening 23 in the foot to feed the fabric rearwardly. The feed dog I is fixed to the front end of a feed lever 33 which extends longitudinally within the frame arm 1. The lever 38 is fulcrumed intermediate its ends by a vertical link 39 to the wall I2 of the arm I, and the rear end of the lever is operatlvely connected to an adjustable eccentric which is indicated as a whole by the numeral 40. The lever 38 is located slightly below the needle shaft 25 and between said shaft and the wall l2 of the frame arm 1, the eccentric 40 being positioned on the main shaft extension 23 between the needle shaft eccentric 30 and said wall [2. The feed dog I is timed with the needle 21 so that when the needle has just withdrawn from the fabric, the feed dog is at the beginning of its feed stroke, as shown in Fig. 16, and when the feed dog is at the end of its feedstroke the needle has begun its penetrating stroke, as shown in Fig. 1'7.

Usually in lock stitch machines, the main shaft is rotated in a direction towards the operator, but in the present case the main shaft is rotated in a direction away from the operator.

The needle thread J is led from any suitable source of supply to a stationary thread guide 4| mounted on the rear end of the frame arm I, thence forwardly around a tension 42 mounted on the front end of the arm 1, thence rearwardly arcane along said arm and through a thread guide or opening 43 formed in the upper end of a take-up. lever K, thence forwardly to a stationary thread uide 44 mounted on the front end of the arm I, thence through a thread guide 45 mounted on the needle arm 28, and thence to the needle eye.

The take-up lever K is fixed to the right hand end of a horizontal rock shaft 43 which is journaled in the upper portion of the oil housing C in front of the main shaft extension 23. The shaft 46 extends transversely of the frame arm 1 and consequently the take-up lever oscillates in a vertical plane extending longitudinally of said arm. The lever projects upwardly through a longitudinally extending slot 41 formed in the arm, and the thread guide or opening 43 is located above said arm. The left hand end of the rock shaft 46 projects into the oil compartment of the oil housing 0 and fixed thereon is a downwardly projecting rock arm 43 which is oscillated from the main shaft extension 23 by means of the following linkage located within said oil compartment:

A supporting link 43 is fulcrumed to swing about a stationary pivot 53 located below the main shaft extension 23. A bell crank lever Si is fulcrumed at its angle as at 52 to the free end of the supporting link 43. This bell crank lever includes arms 53 and 34, the former being pivotally connected at its free end toan eccentric pin 55 mounted on the gear 33, and the latter being pivotally connected at its free end as at I3 to one end of a connecting link 51 which is pivotally connected at its other end as at 53 to the free end of the rock arm 43.

The take-up lever K is swung forwardly to ive slack to the needle thread when the needle loop is being passed around the hook, and is swung rearwardly to take up the slack and set the next to the last formed stitch.

The forward or slack-giving stroke of the takeup lever occurs during 240 of rotation of the main shaft, and the rearward or take-up stroke of the lever occurs during the remaining 121') of rotation of the main shaft. In Fig. 14, I have illustrated the speed travel of the take-up lever during its forward stroke, the line 11 indicating the length of the stroke and the spaced lines 1) indicating the distance of travel of the thread guide or opening 43 of the lever during successive movements of 10., In FigrlSr'I have illustrated the speed travel of the take-up lever during its rearward stroke, the line :1 indicating the length of the stroke and the spaced lines 0 indicating the distance of travel of the thread guide or opening 43 during successive movements of 10. It will therefore be seen that the speed travel of the thread guide 43 is twice as fast during the rearward stroke of the lever as during the forward stroke thereof.

In operation, let it be assumed that the take-up lever is at the rear end of its travel as shown in Fig. 7. Inasmuch as the main shaft rotates in.

an anti-clockwise direction as shown in said Figure, the eccentric pin 55 will be moved 120 and elevated to the position shown in Fig. 8. During this travel of the pin, the supporting link 49 will be swung upwardly until the floating fulcrum 52 of the bell crank lever 5| will be in substantial alinement with the longitudinal axis of the main shaft. Thus it will be seen that the bell crank lever will be elevated and that the connecting link 51 will cause the take-up lever to be swung forwardly to its half way position as shown in said Fig. 8. During the next 120' aromas movement of the eccentric pin II, or from the position shown in Fig. 8 to the position shown in Fig. 9, the take-up lever will be swung forwardly to its extreme forward position, this movement of the take-up lever being brought about by means of the eccentric pin 5! rocking the bell crank lever 5| about its fulcrum 52 which is substantially stationary during this period.

The eccentric pin 55 then moves downwardly and forwardly and then upwardly and forwardly fromthe Fig. 9 position to the Fig. 7 position, during which time the pintravels 120 and the take-up lever is swung rearwardly to itsextreme rear position. 'During the first part of this movement, the downward and forward travel of the movement of the bell crank lever, through the medium of the connecti-g link 51, causes the take-up lever to be swung rearwardly to its half way position as shown in said Fig. 10. Upon continued movement of the pin, the bell crank lever will be rocked on its fulcrum 55. and consequently the arm I4 of saidlever will be swung downwardly and the connecting link 51 will cause the take-up lever to be swung to its extreme rear position as shown in Fig. 7. r

When the needle in moving forwardly is about to enter the hem fold, the take-up lever will begin its forward stroke to'give slack to the needle thread. The needle completes its forward or penetrating stroke and withdraws from the hem fold by the time the take-up lever reaches its extreme forward position. In the meantime, the hook has picked up the needle thread loop and is about ready to drop the same. needle completes its backward stroke and the needle loop is cast from the hook to create the last formed stitch, the take-up lever begins its.

backward or take-up. stroke. when the needle has reached its extreme backward position, the take-up lever is approximately midway of its travel and has taken up substantially all of the needle loop which was cast from the hook. Thus while the needle is partaking of the first portion of its forward or penetrating stroke, the take-up lever is completing its backward stroke and functions to further take up the needle thread loop of said last formed stitch and to set the. next tothe last formed stitch. It will therefore be apparent that if the next to the last formed stitches are set too tight, it will result in puckering the fair side of the body fabric which of course is objectionable.

I have overcome this objection by providing the feed dog I with a front section which functions to clamp the bobbin thread extending diagonally from the next-to-last formed stitch to the bobbin against the fabric during the take-up movement of the take-uplever whereby sufllcient slack in the laid bobbin thread will sufllce to prevent the puckering effect above noted.

To this end, the feed dog I includes a body portion 59 having a stepped front portion forming a resultant toe 80 which projects forwardly from the right hand corner thereof, a recess 6! which is located at the left hand comer of the body portion, and a front transverse wall or edge 82 which merges with said toe and recess. The upper face of the body portion is milled, to form a flat horizontal bearing surface 63 and a transverse shoulder The under face of the body Thus while the' portion is provided with two longitudinally extending feed sections ll, '8 which are spaced apart by a longitudinally extending groove 01, the section I! being located on the left'side of the body portion directly in rear of the recess ii, and the section It being located on the right hand side of the bodyportion and extending under the toe 60, the front end of the groove 8! merging with the front wall 82. A vertically yieldable thread clamping section." is positioned in the recess BI and the under face 09 thereof is smooth and is normally disposed slightly below the plane of the feed sections 85, I. The clamping section B l is supported on thebody portion 58 of the foot. through the medium of a rearwardly extending spring arm III which rests on the bearing surface 83 and is secured to the body portion by a screw II, the rear edge I2 of the arm abutting the shoulder 64 to retain the section against turning.

The take-up lever K, the needle 21. and the feed dog I, are timed as follows: When the needle leaves the fabric on its backward-stroke, the feed begins its feeding stroke, and the take-up IIQVCIJJGB'IHS its backward or take-up stroke. The take-up lever moves'rearwardly during the feed stroke of the dog, but its rearward movement stops at an instant before the completion of said feed stroke. It will be observed, as shown in Fig. 16, that the section 88 of the feed dog when at the beginning of its feeding stroke, is clamping the bobbin thread E, which extends diagonally from the next to last formed needle thread loop to the bobbin, against the fabric. Consequently this portion of the bobbin thread will be clamped by the feed dog during the feeding stroke thereof and. while the take-up lever K is moving rearwardlyto take up the needle loop, the feed dog releasing the bobbin thread an instant before the leverreaches the rear end of its stroke, as shown .in Fig. 1'1, whereby the next to last needle thread loop will be set but without taking up the slack bobbin thread which extends'between the last two formed needle loops. Inorder to retain the ridged fabric against the thrust of the needle, I have provided the presser foot 3 with a cloth retainer L which cooperates with the ridge forming element G and is adjustable longitudinally with respect to the foot, and to guide the inner edge of the hem fold in proper relation to the needle, I have mounted an edge guide M on the cloth retainer for transverse adjustments relative thereto. The foot is provided at its front end with a. bearing lug 13 on the right of the opening 28 of the foot.

Mounted in this lug is a horizontally disposed split bushing ll of steel which projects laterally from the side thereof opposite the opening 28 to form an extendedbearing. A rockshaft 15 is joumaled in the bearing and is provided at its inner end with an eccentric pin". The outer end of the rock shaft is provided with a screwdriver slot 'I'l by means of which the shaft may be rocked, and a set screw." is threadably engaged in the outer end of the bushing to retain the shaft in an adjusted position. The cloth retainer L is formed of thin spring steel, and the front end is provided with spaced bearing eyes l9, 19 which are journaled on the eccentric pin 16, and are retained thereon by a screw 80 which is threaded into the end of the pin. The cloth retainer extends rearwardly into the presser foot opening 28 directly above the ridge forming element G, and the rear edge of the retainer is located immediately in front of the needle path,

the retainer having a portion which overhangs the left edge of the presser foot opening and bears against the upper face of the foot to limit the downward movement of said retainer. A coil spring 81 is disposed around the eccentric pin 16 between the bearing eyes l9, I! of the retainer, one end of the spring bearing downwardly upon the retainer and the other end being anchored in a slot 82 of the bushing. It will therefore be seen that the spring yieldably holds the retainer against the ridge of fabric which is formed by the ridge forming element G, and consequently said ridged fabric is held by the retainer against the thrust of the needle and also against being moved forwardly towards the operator when the oscillatory ridge forming disc G is on its forward stroke. The edge guide M includes a horizontal supporting arm 83 having a slot 84 and is mounted on the cloth retainer L for trans-verse adjustments relative thereto. A screw 85 passes through the slot 84 and into the retainer and functions to retain the guide in any position of adjustment. Integral with the left end of the arm 83 is a depending and forwardly extending edge guiding finger 86 which extends readwardly along and projects below the left hand edge of the retainer L. From the above, it will be observed that the retainer L can be adjusted towards or from the needle path to meet different working conditions; that the edge guide M will be adjusted therewith, and that the edge guide is adjustable transversely relative to the retainer.

It is of course to be understood that the details of structure and arrangement of parts may be variously changed and modified without departing from the spirit and scope of my invention.

I claim:

1. In a blind stitch sewing machine, the combination with a main shaft, of a horizontal presser foot, astitch forming mechanism located above the foot and including a reciprocatory needle and a rotary hook including a bobbin, driving connections between the needle and the main shaft and between the hook and the main shaft, a. reciprocatory take-up element for the needle thread, and driving connections between the take-up element and the main shaft for imparting a take-up stroke to the element during approximately of rotation of the main shaft and a slack giving stroke to the element during the remainder of the rotation of the shaft.

2. In a blind stitch sewing machine, the combination with a main shaft, of a horizontal presser foot, a stitch forming mechanism located above the foot and including a reciprocatory needle and a rotary hook including a bobbin, driving connections between the needle and the main shaft and between the hook and the main shaft, a reciprocatory take-up element for the needle thread, driving connections between the .take-upv element and the main shaft for imparting a takeup stroke to the element during approximately 120 of rotation of the main shaft and a slack giving stroke to the element during the remainder of the rotation of the shaft, a 4-motion top fed dog operating in rear of the needle, and driving connections between the main shaft and the feed dog timed to impart feeding strokes thereto during the take-up strokes of ment.

3. In a blind stitch sewing machine, the combination with a main shaft, of a horizontal presser foot. a stitch forming mechanism located above the foot and including a reciprocatory neethe take-up eledle and a rotary hook including a bobbin, driving connections between the needle and the main shaft and between the hook and the main shaft, 9. reciprocatory take-up element for the needle thread. and driving connections between the take-up element and the main shaft for imparting a take-up stroke to the element during approximately 120" of rotation of the main shaft and a slack giving stroke to the element during the remainder of the rotation of the shaft, the driving connections for the take-up element including a rock shaft to which the element is fixed, an eccentric mounted on the main shaft, a rock arm fixed to the rock shaft, a bell-crank having a shiftable fulcrum, one arm of the bell-crank having pivotal connection with said eccentric, and a link connecting the other arm of the bell-crank lever with said rock arm.

4. In a blind stitch sewing machine, the combination with a main shaft, of a horizontal presser foot, a stitch forming mechanism located above the foot and including a reciprocatory needle and a rotary hook including a bobbin, driving connections between the needle and the main shaft and between the hook and the main shaft, a reciprocatory take-up element for the needle thread, driving connections between the take-up element and the main shaft for imparting a takeup stroke to the element during approximately 120 of rotation of the main shaft and a slack giving stroke to the element during the remainder of the rotation of the shaft, a 4-motion top feed dog operating in rear of the needle, and driving connections between the main shaft and the feed dog timed to impart feed strokes thereto during the take-up strokes of the take-up element, said dog being provided with a clamping section for clamping the bobbin thread leading from the last formed stitch to the bobbin during the feed stroke of said dog whereby an additional amount of bobbin thread will be laid between adjacent thread concatenations.

5. In a blind stitch sewing machine, the combination with a stitch forming mechanism including a reciprocatory needle and a cooperating rotary hook containing a bobbin, a take-up means for the needle thread, and a 4-motion top feed dog operating in rear of the needle, and means for operating the take-up means during the feeding stroke of the feed dog to take up the needle loop of the last formed stitch and to set the nextto-last formed stitch, said dog being provided with a clamping section for clamping the bobbin thread leading from the last formed stitch to the bobbin during the feed stroke of said dog whereby an additional amount of bobbin thread will be laid between adjacent thread concatenations.

6. In a blind stitch sewing machine, the combination with a stitch forming mechanism including a reciprocatory needle and a cooperating rotary hook containing a bobbin, a take-up means for the needle thread, and a 4-motion top feed dogoperating in rear of the needle, and means for operating the take-up means during the feed- 7. In a blind stitch sewing machine, the combination with a stitch forming mechanism including a reciprocatory needle and a cooperating rotary hook containing a bobbin, a take-up means for the needle thread, and a 4-motion top feed dog operating in rear of the needle, and means for operating the take-up means during the feeding stroke of the feed dog to take up the needle loop of the last formed stitch and to set the nextto-last formed stitch, said dog being provided with a body portion having a feeding surface on its under face, a vertically yieldable clamping section mounted on the body portion and disposed in front of the feeding surface for clamping the bobbin. thread leading from the last formed stitch to the bobbin during the feed stroke of said dog whereby an additional amount ofbobbin thread will be laid between adjacent thread concatenations, the lower surface of the section being smooth and disposed slightly below the feeding surface.

8. In a blind stitch sewing machine, the combination with a horizontal presser foot having an opening, of a stitch forming mechanism located above the foot and including a reciprocatory needle, a ridge forming element for projecting a ridge of cloth upwardly through said opening into needle pene'rating position, a cloth retainer mounted on the foot to engage the ridged cloth, and an edge guide mounted on the retainer for transverse adjustments relative thereto.

, 9. In a blind stitch sewing machine, the combination with a horizontal presser foot having an opening, of a stitch forming mechanism located above the foot and including a reciprocatory needle, a ridge forming element for projecting a ridge of cloth upwardly through said opening into needle penetrating position, a cloth retainer mounted for longitudinal adjustments on the foot to engage the ridged cloth, and an edge guide mounted on the retainer for transverse adjustments relative thereto.

CHARLES W. MUEILER. 

